Disappear of item

What I expected to happen was...:
I just want to drop item

What actually happened was...:
my helmet and chestplate desappear.

Steps to Reproduce:
1. Drop 1 item ( Let it be golden sword )
2. Immediately drop another item (Let it be Diamond block )
3. Done, your diamond block was disappear from your hand, but U can build. Its just invisible in inventory.